Subject: Re: [PATCH v15 06/20] nvme-tcp: Add DDP data-path

From: Aurelien Aptel <[email-masked]>
Date: Mon, 18 Sep 2023 21:26:06 +0300

Sagi Grimberg <[email-masked]> writes:
>> @@ -1235,6 +1330,9 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
>>       else
>>               msg.msg_flags |= MSG_EOR;
>>
>> +     if (test_bit(NVME_TCP_Q_OFF_DDP, &queue->flags))
>> +             nvme_tcp_setup_ddp(queue, blk_mq_rq_from_pdu(req));
>
> Didn't we agree that setup_ddp should move to setup time and
> not send time?

We believe we haven't reached a conclusion last time [1].

Moving the setup_ddp() call earlier at setup time is less efficient (up
to ~15% less IOPS) when it does the work on a different CPU.

1: https://lore.kernel.org/all/[email-masked]/